1. Technical Field
The present invention relates to a fluorine-doped tin oxide (FTO) transparent conductive film glass having low resistance and high transmittance and a method of fabricating the same. More particularly, the present invention relates to an FTO transparent conductive film glass used for defogging purposes comprising a glass layer, a dielectric barrier layer, a functional layer, a metal electrode layer, a plastic intermediate layer, and a glass layer, stacked in the order, in which the functional layer comprises an FTO transparent conductive film having low resistance and high transmittance, and a method of fabricating the same.
2. Background Art
Conventionally, electrode materials having high transmittance of visible light have been used to prepare various electrodes of heating resistors for anti-fogging or anti-icing purposes adapted in window glasses of vehicles, airplanes, buildings, etc., or electrodes of display devices such as liquid crystal display devices, plasma display panels, electroluminescence display devices, etc. Such transparent conductive materials include antimony-doped tin oxide (ATO), indium tin oxide (ITO), and the like, in which the ITO having a low specific resistance has been widely used. However, in the event that the ITO transparent conductive film glass is formed by applying heat at about 500° C., electrical properties of the ITO are affected, and its heat resistance, chemical resistance and abrasion resistance, for example, are reduced. Accordingly, extensive research on a fluorine-doped tin oxide (FTO) having high stability under high-temperature and high-voltage, low resistance, and high transmittance has continued to progress.
U.S. Pat. No. 2,566,346 discloses a method of applying a fluoride solution capable of being ionized with a tin compound to a glass substrate heated at about 400° C. U.S. Pat. No. 3,107,177 discloses a method of applying a solution comprising an organic tin compound, 4% hydrochloric solution and an ionizable fluoride to a heated substrate so as to fabricate a transparent, electrically conductive tin oxide thin film having a haze of 1% or less. U.S. Pat. No. 3,677,814 discloses a method in which an organic tin compound having a tin-fluorine bond is formed by pyrolysis. However, the above-described prior art methods have some drawbacks in that as it is difficult to synthesize the organic tin compound used as a main material and the cost of raw material is high, it is difficult to use the organic tin compound for as a windshield for defogging purposes.
As methods of fabricating such a tin oxide film, sputtering, chemical vapor deposition (CVD), and spray methods are known in the art. Here, the first and second methods have drawbacks in that vacuum should be provided, and complicated and expensive equipments for providing gases and precursors are necessary.
U.S. Pat. No. 3,959,565 discloses a method of intermittent spraying a non-aqueous solution in an oxidizing atmosphere to coat a tin oxide. U.S. Pat. Nos. 4,146,657 and 4,500,567 disclose methods of manufacturing an electrically conductive tin oxide thin film by a process of utilizing gaseous chemical compounds. However, the method of intermittent spraying has a drawback in that it requires a lot of processing time, and the methods of utilizing gaseous chemical compounds have a drawback in that the cost of raw material is high. These methods thus are not suitable for preparation of such electrically conductive tin oxide thin film for defogging purposes.
A dielectric barrier layer is disposed between the FTO transparent conductive film and the glass substrate to achieve high transmittance of the windshield. The dielectric barrier layer is introduced to prevent a decrease in transmittance due to change of the color of the windshield which is caused by diffusion of Na ions of the glass layer into the FTO transparent conductive film. Such technologies related to the dielectric barrier layer disposed between the FTO transparent conductive film and the glass substrate are disclosed in U.S. Pat. Nos. 3,378,396, 4,187,336 and 5,028,566. However, the above-described prior art technologies have some drawbacks in that it is difficult to continuously form the transparent conductive film on the dielectric barrier layer and thus the processing speed is very low. Accordingly, the prior art technologies are not suitable for preparing the transparent conductive film as the windshield for defogging purposes.
Although warm air can be used to defog the windshield, it takes a lot of time and it is necessary to operate an air conditioner for a vehicle. To solve the this problem, a wire type window defogging system was proposed, in which fine metal lines are arranged on the plastic intermediate layer such as polyvinyl butyral (PVB) and electricity is applied thereto to generate heat. However, it is difficult to apply such a system to the windshield because it can reduce visibility. Moreover, in the case where an electrode material such as Ag and ITO is thinly coated, the electrode material cost and the manufacturing cost can be highly increased.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.